In the production of printed circuit boards, for example, as disclosed in U.S. Pat. No. 4,253,360, various electronic components have lead wires which project through corresponding holes within the board, and the lead wires are secured to the board by solder which fills the holes and connects the lead wires to metal conductor strips formed on the outer surface of the board. As disclosed in the above patent, it is desirable to cut or shear the lead wires close to the outer surface of the printed circuit board so that the cutting blade also shears through the solder fillets surrounding the lead wires to reduce the problem of "flagging" caused by the lead wires folding over or bending before the lead wire is completely sheared or severed.
In the above patent, it is disclosed that the "flagging" problem is avoided by providing the beveled cutting edge of the rotary blade with unevenly spaced notches. In any event, the flagging problem requires substantial labor by inspectors to locate and remove the folded over end portions of the lead wires so that the end portions do not bridge the conductor strips and cause a short circuit. In order to prevent the end portions of the lead wires from remaining on the printed circuit board after the lead end portions are severed, some trimming machines provide for supporting the circuit board horizontally with the lead wires projecting downwardly during the cut-off or trimming operation, for example, as disclosed in U.S. Pat. Nos. 3,307,442 and 3,453,918. However, larger circuit boards present a problem of sagging in the middle requiring that the cutter block be spaced further from the board.
It has been found that in the production of printed circuit boards in high volume, there are variations in the thickness of the printed circuit boards, for example, variation over 0.010 inch. Accordingly, the beveled cutting edge of the cut-off blade is usually spaced from the circuit board by a sufficient distance to accommodate the variations in the thickness of the printed circuit boards. However, as mentioned above, it has been found desirable to shear the lead wires very close to the outer surface of the printed circuit board, for example, on the order of 0.010 inch, so that the beveled edge of the cutting blade shears not only through the lead wires but also through the fillets of solder for substantially eliminating the "flagging" problem.